Metallocenes constitute useful compounds for olefin polymerizations when combined with a cocatalyst such as aluminoxane. It is generally accepted that the properties of the polymers formed using such a combination are determined in large part by the structural nature of the metallocene, including its steric and electronic features. Therefore, there is a need to develop new methods to prepare metallocenes that allow an assortment of diverse substituents to be incorporated into the metallocene structure.
Fulvenes, having the general formula C4R″4C═CRR′ and the structure
are often-useful precursors to metallocenes and can provide a means for integrating a range of substituents into the metallocene structure. One aspect of this utility can be seen from the reaction of fulvenes with cyclopentadienyl-, indenyl-, and fluorenyl-lithium reagents as illustrated in Scheme 1, because the resulting products can be used as ligand precursors to form bridged or ansa-metallocenes. Ansa-metallocene catalysts are useful in olefin polymerizations and copolymerizations, in part because of impact the tailored ligand set can have on the properties of the resulting polymer.

Therefore, it is of interest to develop new methods to prepare fulvenes that may provide these ligands in higher yields or with greater selectively. It is also of interest to develop new methods to prepare ansa-metallocenes based on new fulvene synthetic methods.